If I'm not wrong, all you have to do is use the distributive property.
8.88 I think. Hope this helps :)
I and 4i
let's say if you have i you can automatically think there is a one in front of it so one term like this (i) could look like this 1i and any number with the same variable or letter are like terms
hope this helps
4 years apart if he is 20 years old